DE102008036985B4 - Laser driver circuit, method of controlling a laser driver circuit and use - Google Patents

Abstract

Laser driver circuit
- having an amplifier device (100) with a plurality of switchable sub-amplifiers (101, ..., 116), which are connectable or connected to an output (190) for a connection of a laser,
With an analog switching device (200) for switching analog input signals,
With a plurality of analog inputs (i1, i2, i3) for the analog input signals,
With a plurality of control inputs (w1, w2, w3) for receiving digital control signals,
In which each switchable sub-amplifier (101, ..., 116) has a switching device (1012, ..., 1162) for switching the amplification by one of the digital control signals,
With a digital switching device (1000, 1011,..., 1161) connected to an input of each switching device (1012,..., 1161) for selectably connecting the input of the switching device (1012,..., 1162) of each switchable sub-amplifier ( 101, ..., 116) having a control input (w1, w2, w3),
- In which each switchable sub-amplifier (101, ..., 116) has an analog input, which with the analog switching device ...

Description

The The present invention relates to a laser driver circuit, a method for controlling a laser driver circuit and a use.

For storage drives in which so-called compact discs are provided as storage media are laser semiconductor diodes used to read information from the storage media or to describe this. Depending on the used technology of the storage medium thereby laser diodes in different wavelength ranges needed. To read or write information to a storage medium defined light pulses are required by the laser diode be emitted. The impulses have to in doing so to the laser diode used and to the storage medium used be adjusted. Such an adaptation may be in the case of a write operation be referred to as a writing strategy.

From the US 2005/0047316 A1 is a circuit for controlling the performance of a laser for an optical drive known. For driving the laser current, a laser driver is provided. The laser driver has three current amplifiers for fixed gain amplification, summing the output currents of the amplifiers. The current amplifiers are designed to switch their output current on and off at high speed. For this purpose, signals of a write pulse generator control the current amplifiers. The circuit comprises a switching unit configured to select which of the signals of the write pulse generator turns on and off which of the output currents of the current amplifiers. Other circuits are from the US 2007/0036056 A1 . US 2007/0147450 A1 . US 2007/0096963 A1 . US 2002/0114364 A1 . US 2003/0048821 A1 . US 2007/0280316 A1 and the US Pat. No. 6,400,673 B1 known, showing various embodiments of the control of laser diodes by means of digital-to-analog converter.

Around an output current for can drive the laser diode several individual streams to summate a current pulse before amplification, so that a single amplifier that Output current provides. The area of the output amplifier the semiconductor chip is determined by the height of the maximum output current certainly. Also can the individual streams strengthened separately and after the reinforcement summed by one amplifier each become. The area every amplifier is there for to design the maximum output current of the same. In bipolar technology a common output amplifier can be easily realized while in CMOS technology output amplifier for the required high speed in a fundamentally different circuit technology be realized in bipolar technology.

Of the The invention is based on the object of a driver circuit for a laser diode as possible improve.

These Task is by a laser driver circuit with the features of the independent Claim 1 solved. Advantageous developments are the subject of dependent claims and included in the description.

As a result, a laser driver circuit is provided which is designed output current pulses for one To drive semiconductor laser diode. The current pulses are preferably defined in their form provided by the laser driver circuit, wherein the defined form - that is the course and the amplitude and the length of the current pulse - advantageously is variably adjustable. Preferably, the laser driver circuit monolithically integrated on a semiconductor chip.

The Laser driver circuit has a plurality of control inputs to Reception of digital control signals. The control inputs form a digital parallel interface for parallel reception of the digital control signals. The digital control signals serve define the shape of the current pulses, the digital control signals the different control inputs to each other have a different pulse length and / or each other may be delayed. The parameters of the digital control signals are for example by a signal generation circuit connectable to the laser driver circuit adjustable.

The The laser drive circuit includes a repeater device having a plurality of switchable sub amplifiers on that with an exit for a connection of a laser can be connected or connected. Preferably is the amplifier device designed to switch one or more analog input signals and to reinforce. The analog outputs are preferred the switchable subamplifier connected with each other. Output currents of the sub amplifiers preferably summed in one or more stream summation nodes. Advantageously, the output is a pin for connecting a semiconductor laser diode educated. The switchable sub-amplifiers are preferably as switchable current amplifier or switchable transconductance amplifiers formed in particular in CMOS technology.

The laser driver circuit has an analog switching device. The analog switching device is for switching analog input signals to a plurality of analog inputs for the analogs formed gear signals. Preferably, variable currents or voltages which are constant within a pulse are applied to the analog inputs. For switching, the analog switching device has switching means, such as analog multiplexers.

Everyone Switchable sub-amplifiers has a switching device for switching the gain. The Switching device is for example a means of a transistor switchable current mirror. The gain is preferably a and can be switched off. Each switchable sub-amplifier is for switching through a the digital control signals formed.

The Laser driver circuit has one with an input of each switching device connected digital switching device on. The digital switching device is to selectable Connection of the input of the switching device with a control input educated. Preferably, the digital switching device is formed exactly one of the control inputs to Select connection or to select no control input. As a result, the selection of a control input will affect the associated digital input signal on the switching operations in the associated subamplifiers the amplifier device out. If no control input is selected, the associated subamplifier is deactivated.

Everyone Switchable sub-amplifiers has an analog input connected to the analog switching device for switching an analog input signal to the analog input is. Preferably, the analog input of each sub-amplifier is on the analog switching device connected directly. Alternatively it is it possible for switching the analogue input signal to the analogue input of the part amplifier the analog input signal in addition amplified by an intermediate amplifier.

Of the Invention is still based on the task as possible to provide an improved method for controlling a laser driver circuit.

These The object is achieved by the method having the features of the independent claim 7 solved. Advantageous developments are the subject of dependent claims and included in the description.

As a result, For example, a method for controlling a laser driver circuit is provided. The laser driver circuit has analog inputs and digital control inputs and an amplifier device with a plurality of switchable sub amplifiers.

In According to the method, each switchable subamplifier will not be one or exactly one digital control input assigned by driving a multiplexer.

Everyone Switchable sub-amplifiers is no or exactly one analog input by controlling a Assigned analog multiplexer.

Of the Invention is further based on the object, a use specify.

These The object is achieved by a use having the features of the independent claim 9 solved. Advantageous developments are the subject of dependent claims and indicated in the description.

As a result, is a use of a plurality of individually switchable sub-amplifiers one amplifier device for providing an output current to a laser by current summation the output currents the switchable subamplifier intended.

to Providing the output current are several switchable sub-amplifiers by means of Multiplexer with exactly one digital control input and by means of Analog multiplexer connected to exactly one analog input. Preferably The multiplexer and the analog multiplexer are driven dependent on each other.

The The developments described below relate both on the laser driver circuit, as well as on the use as well to the method for controlling a laser driver circuit.

According to one preferred development, the digital switching device has a Number of multiplexers. The respective multiplexer is preferred to the entrance of the associated Switching device connected. The multiplexers are preferred with the control inputs directly or via a logic, for example indirectly connected for release. alternative For multiplexing, the digital switching device may have transistor logic or gate logic applied to each input of the switching devices the sub amplifier connected.

According to one advantageous embodiment, the analog switching device has a Plurality of analog multiplexers. Preferably, each analog multiplexer is connected to exactly one analog input of an associated switchable sub-amplifier.

In a particularly preferred development, the laser driver circuit has a control circuit which is designed to set the multiplexers of the subamplifiers of the amplifier device is. Preferably, the control circuit is connected to a digital input of the amplifier device for adjustment. In another advantageous embodiment which can also be combined, it is provided that the control circuit is designed to set the analog multiplexer. Preferably, the control circuit is connected to a digital input of the analog switching device for adjustment.

The Control circuit may for example have a logic for adjustment. Preferably, the control circuit has a plurality of registers each register being a multiplexer of a sub-amplifier and / or an analog multiplexer of the analog switching device is assigned. has the multiplexer, for example, four switching position, this indicates associated Register at least a two-bit width to set all four Switch positions on.

According to one advantageous embodiment are analog outputs of all sub-amplifiers for Current summation with the output for connected to the connection of the laser. To stream summation can thereby one or more stream summing nodes may be provided which support the Current of the sub-amplifiers to merge.

Prefers is provided that the assignment of each switchable sub-amplifier to no or exactly one digital control input by means of a register value is stored in a memory of the laser driver circuit. Preferably the assignment of each switchable sub-amplifier is none or accurate an analog input stored by means of a register value. Advantageously the assignments to the digital control input and to the analog input Logically linked together.

Preferably are the sub amplifiers the same education.

The training variants described above are both individually as well as in combination particularly advantageous. All can Training variants are combined with each other. further developments of the method or the use arise, for example Functions of the laser driver circuit. Some possible combinations are in the description of the embodiments of the figures explained. These options shown there However, combinations of the training variants are not finally.

in the Below, the invention will be described by way of example with reference to drawings Representations closer explained.

there demonstrate

1 a schematic representation of a laser driver circuit of a first embodiment, and

2 a schematic representation of a laser driver circuit of a second embodiment.

In 1 a laser driver circuit is shown schematically by a block diagram. The laser driver circuit has an amplifier device 100 , an analog switching device 200 , a digital switching device 1000 and a control circuit 300 on. The analog switching device 200 is connected to a plurality of analog inputs i1, i2 and i3. In the embodiment of 1 the analog inputs i1, i2 and i3 are designed as current inputs. The analog switching device 200 has a plurality of (fourteen) analog outputs connected to analog inputs of the amplifier device 100 are connected. The analog switching device 200 is designed to switch each of its analog outputs to none or exactly one of the analog inputs i1, i2 or i3.

Each analog input of the amplifier device 100 is a switchable subamplifier 101 to 114 assigned. Each analogue output of each subamplifier 101 to 114 is with the connection 190 for connecting a semiconductor laser diode (in 1 not shown). For switching the switchable sub-amplifiers 101 to 114 is the amplifier device 100 via the digital switching device 1000 with control inputs w1, w2, w3 connected via the dynamic digital control signals, the individual sub-amplifiers 101 to 114 turn. For this purpose, the digital switching device 1000 a multiplex function, whereby each switchable sub-amplifier 101 to 114 with no or exactly one control input w1 or w2 or w3 is connectable. Thus, a switchable sub-amplifier 101 to 114 not simultaneously connected to two control inputs, so that at the same time only the selection of a single control input or no control input is possible.

The two multiplexing functions of the analog switching device 200 and the digital switching device 1000 are through the control circuit 300 controllable. This is the control circuit 300 through a first connection 310 with an input of the digital switching device 1000 and through a second connection 320 with the analog switching device 200 connected. Preferably, the control circuit 300 Register whose register values the switching positions of multiplexers of the digital switching device 1000 and the analog switching device 200 establish.

Preferably, the switching positions of the digital switching device 1000 and the analog switch contraption 200 associated with each other. For example, the first sub-amplifier 101 connected to the first control input w1 for switching by the control signal of the first control input. At the same time, the analog switching device 200 switched such that the analog input of the first sub-amplifier 101 via the analog switching device 200 is connected to the first analog input i1. If the assignment of analog input i1, i2, i3 to the control inputs w1 or w2 or w3 is fixed, the connection is established via both connections 310 and 320 transmit the same signal, so that both connections 310 and 320 also be connected to each other.

Furthermore, the control circuit 300 a serial or parallel interface 330 , For example, a bus interface, via which the register values can be written or read in the registers. the interface 330 For example, it may form a connection to a microcontroller (not shown), which may be monolithically integrated with the laser driver circuit on a semiconductor chip. The analog inputs i1, i2, i3 may be connected to amplifiers, digital-to-analog converters and / or current sources, which are advantageously monolithically integrated together with the laser driver circuit on a semiconductor chip. The control inputs w1, w2, w3 are advantageously connected to a signal generation circuit and / or a digital logic, which are advantageously monolithically integrated together with the laser driver circuit on a semiconductor chip. Alternatively, it is possible to connect circuits to the pins of the laser driver circuit connected to the control inputs w1, w2, w3 and analog inputs i1, i2, i3.

In 2 another embodiment of a laser driver circuit is shown schematically. The amplifier device 100 has sixteen switchable sub-amplifiers in this embodiment 101 to 116 on. The sub amplifiers 101 to 116 are all about a stream summation node with an output 190 for a connection of a semiconductor laser (not shown). Each switchable sub-amplifier 101 to 116 has a switching device 1012 to 1162 for example in the form of a switchable transconductance amplifier or a switchable current mirror for current amplification. The analog input of the switching device 1012 to 1162 each sub-amplifier 101 to 116 is with an analog switching device 200 connected.

In the embodiment of 2 is a digital switching device through multiple multiplexers 1011 to 1161 formed, each multiplexer 1011 to 1161 in a sub-amplifier 101 to 116 is integrated. Each multiplexer 1011 to 1161 is with an input of the associated switching device 1012 to 1162 and connected to each control input w1, w2 and w3 of the laser driver circuit. By means of a control via a 2-bit line, the switching position of the respective multiplexer 1011 to 1161 be switched between exactly one of the three control inputs w1 or w2 or w3 or a switching position without a connection to the control inputs. For this, the two control bits become static in a register in the control circuit 300 saved. Thus, for sixteen multiplexers 1011 to 1161 the sixteen sub amplifier 101 to 116 a 32-bit wide control connection is required around all multiplexers 1011 to 1161 to control independently of each other.

By programming the register values of the registers in the control circuit 300 it is possible for each dynamic control signal at one of the control inputs w1, w2 and w3, respectively, by the number of switched sub amplifiers 101 , ..., 116 to assign a maximum output current or a scaling factor. Activation of sub amplifiers not only changes the maximum output current, but also an amplification factor, which can be called scaling. The effect is that the respective maximum output current is always (reproducibly) achievable with the same input current.

Compared to conventional laser drivers are by the embodiment of 2 achieved several advantages. For the amplification function, a smaller chip area is needed in total. Dynamic properties are improved. In addition, the scaling function achieves a higher resolution at low output currents.

According to the connection 320 and the entrance 230 the analog multiplexers 2010 to 2160 statically controlled, so that corresponding analog inputs i1, i2, i3 for analog signals - such as static currents - through the respective analog multiplexer 2010 to 2160 with an analog output 2011 to 2161 the analog switching device 200 get connected. Consequently, each switchable sub-amplifier has 101 , ..., 116 an analog input connected to the analog switching device 200 for switching an analog input signal i1, i2, i3 to the analog input of the switchable subamplifier 101 , ..., 116 connected is.

For example, it is possible the control input w1, the first eight sub-amplifier 101 to 108 assign, so that the control signal at the first control input w1 the eight sub-amplifiers 101 to 108 on. The second control input w2 are correspondingly six further sub-amplifiers 109 to 114 assigned. The third control input w3 becomes the fifteenth sub-amplifier 115 assigned. The sixteenth sub-amplifier 116 is not assigned to a control input. With this program tion is the lowest output current through the third control signal w3 so only by the sub-amplifier 115 and the largest output current through the common simultaneous control signals w1 and w2 and w3 thus through the sub-amplifiers 101 to 115 possible.

This causes the surprising effect that over-sizing of the amplifier device 100 is not required. The amplifier device 100 must be designed only for the maximum power required, regardless of how large the sub-contributions are to be effected by the individual control signals w1, w2, w3. The sub-contributions can be made by the flexible assignment of the switchable sub-amplifiers 101 to 116 be customized for each laser diode type.

The invention is not limited to the illustrated embodiments of the 1 or 2 limited. For example, it is possible to provide a larger or smaller number of sub amplifiers. It is also possible to connect further analog stages to the analog inputs i1, i2, i3. It is also possible to connect the control inputs with digital logic. It is also possible for a plurality of laser diodes to provide a plurality of amplifier devices or a switchover of the amplifier device to a plurality of outputs.

100

amplifier device

101 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116

switchable subamplifiers

130 230

entrance

1000

Digital switching device

1011 1021, 1031, 1041, 1051, 1061, 1071, 1081, 1091, 1101, 1111, 1121, 1131, 1141, 1151, 1161

multiplexer

1012 1022, 1032, 1042, 1052, 1062,

Switching device, switchable

1072, 1082, 1092, 1102, 1112, 1122, 1132, 1142, 1152, 1162

current mirror

190

Output, Pin code

200

Analog switching device

2010 2020, 2030, 2040, 2050, 2060, 2070, 2080, 2090, 2100, 2110, 2120, 2130, 2140, 2150, 2160

analog multiplexer

2011 2021, 2031, 2041, 2051, 2061, 2071, 2081, 2091, 2101, 2111, 2121, 2131, 2141, 2151, 2161

output

300

control circuit

310 320

connection

330

Interface, bus

i1, i2, i3

analog input

w1, w2, w3

control input

Claims (9)

Laser driver circuit - with an amplifier device ( 100 ) with a plurality of switchable sub amplifiers ( 101 , ..., 116 ), which have an output ( 190 ) can be connected or connected for a connection of a laser, - with an analog switching device ( 200 ) for switching analog input signals, - having a plurality of analog inputs (i1, i2, i3) for the analog input signals, - having a plurality of control inputs (w1, w2, w3) for receiving digital control signals, - each switchable subamplifier ( 101 , ..., 116 ) a switching device ( 1012 , ..., 1162 ) for switching the gain by one of the digital control signals, - having one with an input of each switching device ( 1012 , ..., 1162 ) connected digital switching device ( 1000 . 1011 , ..., 1161 ) for the selectable connection of the input of the switching device ( 1012 , ..., 1162 ) of each switchable sub-amplifier ( 101 , ..., 116 ) with a control input (w1, w2, w3), - in which each switchable sub-amplifier ( 101 , ..., 116 ) has an analog input connected to the analog switching device ( 200 ) is connected to selectably switch an analog input signal to the analog input. Laser driver circuit according to claim 1, wherein the digital switching device comprises a number of multiplexers ( 1011 , ..., 1161 ), each multiplexer ( 1011 , ..., 1161 ) each to the input of the switching device ( 1012 , ..., 1162 ) connected. Laser driver circuit according to one of the preceding claims, - in which the analog switching device ( 200 ) a plurality of analog multiplexers ( 2010 , ..., 2160 ), each analog multiplexer ( 2010 , ..., 2160 ) to an analog input of an associated switchable sub-amplifier ( 101 , ..., 116 ) connected. Laser driver circuit according to one of the preceding claims, - with a control circuit ( 300 ) used to set the multiplexers ( 1011 , ..., 1161 ) of the subamplifier ( 101 , ..., 116 ) of the amplifier device ( 100 ) with an input ( 130 ) of the amplifier device ( 100 ) and / or to set the analog multiplexer ( 2010 , ..., 2160 ) with an input ( 230 ) of the analog switching device ( 200 ) connected is. Laser driver circuit according to claim 4, - in which the control circuit ( 300 ) has a plurality of registers, each register being a multiplexer ( 1011 , ..., 1161 ) of a sub-amplifier ( 101 , ..., 116 ) assigned. Laser driver circuit according to one of the preceding claims, - in the analog outputs of all sub-amplifiers for current summation with the output ( 190 ) are connected for the connection of the laser. Method for controlling a laser driver circuit with analog inputs (i1, i2, i3) and digital control inputs (w1, w2, w3) and with an amplifier device ( 100 ) with a plurality of switchable sub amplifiers ( 101 , ..., 116 ), - in which each switchable sub-amplifier ( 101 , ..., 116 ) no or exactly one digital control input (w1, w2, w3) by means of a multiplexer ( 1011 , ..., 1161 ), in which each switchable sub-amplifier ( 101 , ..., 116 ) no or exactly one analog input (i1, i2, i3) by means of an analog multiplexer ( 2010 , ..., 2160 ). Method according to Claim 7, - in which the assignment of each switchable sub-amplifier ( 101 , ..., 116 ) is stored to no or exactly one digital control input (w1, w2, w3) by means of a register value, and - in which the assignment of each switchable sub-amplifier ( 101 , ..., 116 ) is stored to no or exactly one analog input (i1, i2, i3) by means of a register value. Use of a plurality of individually switchable sub amplifiers ( 101 , ..., 116 ) an amplifier device ( 100 ) for providing an output current for a laser by current summation of the output currents of the switchable sub-amplifiers ( 101 , ..., 116 ), in which a plurality of switchable sub-amplifiers ( 101 , ..., 116 ) by means of multiplexer ( 1011 , ..., 1161 ) with exactly one digital control input (w1, w2, w3) and by analog multiplexer ( 2010 , ..., 2160 ) with exactly one analog input (i1, i2, i3).